$$(4x+5y)^{7}$$
$16384x^{7}+1400000x^{3}y^{4}+1050000x^{2}y^{5}+437500xy^{6}+78125y^{7}+1120000y^{3}x^{4}+537600y^{2}x^{5}+143360yx^{6}$
$\left(4x+5y\right)^{7}$
